Interference pigments on the basis of silicon oxides

ABSTRACT

The present invention relates to pigments, the particles of which generally have a length of from 2 μm to 5 mm, a width of from 2 μm to 2 mm, and a thickness of from 20 nm to 2 μm, and a ratio of length to thickness of at least 2:1, wherein the particles contain a core of SiO y  with 0.70≦y≦1.8, especially 1.40≦y≦1.8, having two substantially parallel faces, the distance between which is the shortest axis of the core, comprising (a) a material, especially a metal oxide, having a high index of refraction; or (a) a thin semi-transparent metal layer; a process for their production and their use in paints, ink-jet printing, for dyeing textiles, for pigmenting coatings (paints), printing inks, plastics, cosmetics, glazes for ceramics and glass.

The present invention relates to (interference) pigments having a coreof SiO_(y) with 0.70≦y≦1.95, especially 1.1≦y≦1.8, comprising a metaloxide having a high index of refraction or a thin semi-transparent metallayer, a method of producing the interference pigments and their use inpaints, ink-jet printing, for dyeing textiles, for pigmenting coatings,printing inks, plastics, cosmetics, glazes for ceramics and glass.

Interference pigments having a core of SiO₂ are known (Gerhard Pfaff andPeter Reynders, Chem. Rev. 99 (1999) 1963-1981):

-   -   The SiO₂ flakes are produced, for example, by a process        described in WO93/08237, wherein a sodium water glass solution        is applied as a thin film on an endless band, solidified and        dried. WO93/08237 also describes the coating of the SiO₂ flakes        with a metal oxide having a high index of refraction or a thin        semi-transparent metal layer.

WO98/53011 discloses multi-coated interference pigments consisting of atransparent carrier material which is coated with alternating metaloxide layers with a high and low refractive index, wherein thedifference between the respective refractive indexes is 0.1. The metaloxide layers are obtained in a wet process by hydrolysis of thecorresponding water-soluble metal compounds, by separating, drying andoptionally calcinating the pigment thus obtained.

WO01/57287 describes a process comprising the production of a substratematerial, for example, silicon oxide, by physical vapor deposition andthe wet chemical coating of the obtained flakes with, for example, TiO₂.According to Example 4 of WO01/57287 silicon oxide flakes having athickness of 200 nm and a particle size of 1 to 100 μm are obtained byPVD and then coated by a wet chemical process with TiO₂.

EP-A-803549 discloses coloured pigments containing (a) a core consistingof an essentially transparent or metallic reflecting material, and (b)at least a coating consisting essentially of one or more siliconeoxides, the molar ratio of oxygen to a silicon being 0.25 to 0.95;

It is the object of the present invention to provide interferencepigments, having higher color strength and color purity as compared withinterference pigments known from the state of the art.

Said object has been solved by pigments, the particles of whichgenerally have a length of from 2 μm to 5 mm, a width of from 2 μm to 2mm, and a thickness of from 20 nm to 2 μm, and a ratio of length tothickness of at least 2:1, wherein the particles contain a core ofSiO_(y) with 0.70≦y≦1.95, especially 1.1≦y≦1.8, most preferred1.4≦y≦1.8, having two substantially parallel faces, the distance betweenwhich is the shortest axis of the core, comprising (a) a material,especially a metal oxide, having a high index of refraction, orpigments, the particles of which generally have a length of from 2 μm to5 mm, a width of from 2 μm to 2 mm, and a thickness of from 20 nm to 2μm, and a ratio of length to thickness of at least 2:1, wherein theparticles contain a core of SiO_(y) with 0.70≦y≦1.95, especially1.1≦y≦1.8, most preferred 1.4≦y≦1.8, having two substantially parallelfaces, the distance between which is the shortest axis of the core,comprising

-   -   (a) a thin semi-transparent metal layer.

The term “SiO_(y) with 0.70≦y≦1.95” means that the molar ratio of oxygento silicon at the average value of the silicon oxide layer is from 0.70to 1.95. The composition of the silicon oxide layer can be determined byESCA (electron spectroscopy for chemical analysis).

According to the present invention the term “aluminum” comprisesaluminum and alloys of aluminum. Alloys of aluminum are, for exampledescribed in G. Wassermann in Ullmanns Enzyklopädie der IndustriellenChemie, 4. Auflage, Verlag Chemie, Weinheim, Band 7, S. 281 to 292.Especially suitable are the corrosion stable aluminum alloys describedon page 10 to 12 of WO 00/12634, which comprise besides of aluminumsilicon, magnesium, manganese, copper, zinc, nickel, vanadium, lead,antimony, tin, cadmium, bismuth, titanium, Chromium and/or iron inamounts of less than 20% by weight, preferably less than 10% by weight.

Suitable metals for the semi-transparent metal layer are, for example,Cr, Ti, Mo, W, Al, Cu, Ag, Au, or Ni. The semi-transparent metal layerhas typically a thickness of between 5 and 25 nm, especially between 5and 15 nm. The SiO_(y) substrates can have a metal layer only on oneparallel surface, but preferably the metal layer is present on bothparallel faces of the substrate.

The metal/SiO_(y)/metal flakes are prepared by a PVD process comprisingthe steps:

-   -   a) vapour-deposition of a separating agent onto a (movable)        carrier to produce a separating agent layer,    -   b) vapour-deposition of a metal layer onto the separating agent        layer,    -   c) vapour-deposition of an SiO_(y) layer onto the metal layer,        wherein 0.70≦y≦1.80,    -   d) vapour-deposition of a metal layer onto the SiO_(y) layer,    -   e) dissolution of the separating agent layer in a solvent, and    -   f) separation of the metal/SiO_(y)/metal flakes from the        solvent.

Alternatively the metal layer can be obtained by wet chemical coating orby chemical vapor deposition, for example, gas phase deposition of metalcarbonyls. The substrate is suspended in an aqueous and/or organicsolvent containing medium in the presence of a metal compound and isdeposited onto the substrate by addition of a reducing agent. The metalcompound is, for example, silver nitrate or nickel acetyl acetonate(WO03/37993).

According to U.S. Pat. No. 3,536,520 nickel chloride can be used asmetal compound and hypophosphite can be used as reducing agent.According to EP-A-353544 the following compounds can be used as reducingagents for the wet chemical coating: aldehydes (formaldehyde,acetaldehyde, benzalaldehyde), ketones (acetone), carbonic acids andsalts thereof (tartaric acid, ascorbinic acid), reductones(isoascorbinic acid, triosereductone, reductine acid), and reducingsugars (glucose).

If semi-transparent metal layers are desired, the thickness of the metallayer is generally between 5 and 25 nm, especially between 5 and 15 nm.

If pigments with metallic appearance are desired, the thickness of themetal layer is >25 nm to 100 nm, preferably 30 to 50 nm. If pigmentswith colored metal effects are desired, additional layers of colored orcolorless metal oxides, metal nitrides, metal suldfides and/or metalscan be deposited. These layers are transparent or semi-transparent. Itis preferred that layers of high index of refraction and layers of lowindex of refraction alternate or that one layer is present, whereinwithin the layer the index of refraction is gradually changing. It ispossible for the weathering resistance to be increased by means of anadditional coating, which at the same time causes an optimal adaption tothe binder system (EP-A-268918 and EP-A-632109).

In one preferred embodiment of the present invention, the interferencepigments comprise materials having a “high” index of refraction, whichis defined herein as an index of refraction of greater than about 1.65,and optionally materials having a “low” index of refraction, which isdefined herein as an index of refraction of about 1.65 or less. Various(dielectric) materials that can be utilized including inorganicmaterials such as metal oxides, metal suboxides, metal fluorides, metaloxyhalides, metal sulfides, metal chalcogenides, metal nitrides, metaloxynitrides, metal carbides, combinations thereof, and the like, as wellas organic dielectric materials. These materials are readily availableand easily applied by physical, or chemical vapor deposition processes,or by wet chemical coating processes.

In an especially preferred embodiment, the interference pigments on thebasis of the silicon oxide substrate comprises a further layer of adielectric material having a “high” refractive index, that is to say arefractive index greater than about 1.65, preferably greater than about2.0, most preferred greater than about 2.2, which is applied to theentire surface of the silicon/silicon oxide substrate. Examples of sucha dielectric material are zinc sulfide (ZnS), zinc oxide (ZnO),zirconium oxide (ZrO₂), titanium dioxide (TiO₂), carbon, indium oxide(In₂O₃), indium tin oxide (ITO), tantalum pentoxide (Ta₂O₅), chromiumoxide (Cr₂O₃), cerium oxide (CeO₂), yttrium oxide (Y₂O₃), europium oxide(Eu₂O₃), iron oxides such as iron(II)/iron(III) oxide (Fe₃O₄) andiron(III) oxide (Fe₂O₃), hafnium nitride (HfN), hafnium carbide (HfC),hafnium oxide (HfO₂), lanthanum oxide (La₂O₃), magnesium oxide (MgO),neodymium oxide (Nd₂O₃), praseodymium oxide (Pr₆O₁₁), samarium oxide(Sm₂O₃), antimony trioxide (Sb₂O₃), silicon monoxides (SiO), seleniumtrioxide (Se₂O₃), tin oxide (SnO₂), tungsten trioxide (WO₃) orcombinations thereof. The dielectric material is preferably a metaloxide. It being possible for the metal oxide to be a single oxide or amixture of oxides, with or without absorbing properties, for example,TiO₂, ZrO₂, Fe₂O₃, Fe₃O₄, Cr₂O₃ or ZnO, with TiO₂ being especiallypreferred.

It is possible to obtain pigments that are more intense in colour andmore transparent by applying, on top of the TiO₂ layer, a metal oxide oflow refractive index, such as SiO₂, Al₂O₃, AlOOH, B₂O₃ or a mixturethereof, preferably SiO₂, and optionally applying a further TiO₂ layeron top of the latter layer (EP-A-892832, EP-A-753545, WO93/08237,WO98/53011, WO9812266, WO9838254, WO99/20695, WO00/42111, andEP-A-1213330). Nonlimiting examples of suitable low index dielectricmaterials that can be used include silicon dioxide (SiO₂), aluminumoxide (Al₂O₃), and metal fluorides such as magnesium fluoride (MgF₂),aluminum fluoride (AlF₃), cerium fluoride (CeF₃), lanthanum fluoride(LaF₃), sodium aluminum fluorides (e.g., Na₃AlF₆ or Na₅Al₃F₁₄),neodymium fluoride (NdF₃), samarium fluoride (SmF₃), barium fluoride(BaF₂), calcium fluoride (CaF₂), lithium fluoride (LiF), combinationsthereof, or any other low index material having an index of refractionof about 1.65 or less. For example, organic monomers and polymers can beutilized as low index materials, including dienes or alkenes such asacrylates (e.g., methacrylate), polymers of perfluoroalkenes,polytetrafluoroethylene (TEFLON), polymers of fluorinated ethylenepropylene (FEP), parylene, p-xylene, combinations thereof, and the like.Additionally, the foregoing materials include evaporated, condensed andcross-linked transparent acrylate layers, which may be deposited bymethods described in U.S. Pat. No. 5,877,895, the disclosure of which isincorporated herein by reference.

Accordingly, preferred interference pigments comprise besides (a) ametal oxide of high refractive index in addition and (b) a metal oxideof low refractive index, wherein the difference of the refractiveindices is at least 0.1.

Pigments on the basis of silicon oxide (SiO_(y)) substrates, which havebeen coated by a wet chemical method, in the indicated order areparticularly preferred:

-   -   TiO₂ (substrate: silicon oxide; layer: TiO₂, preferably in the        rutile modification), (SnO₂)TiO₂, Fe₂O₃, Fe₃O₄, TiFe₂O₅, Cr₂O₃,        ZrO₂, Sn(Sb)O₂, BiOCl, Al₂O₃, Ce₂S₃, MoS₂, Fe₂O₃.TiO₂        (substrate: silicon oxide mixed layer of Fe₂O₃ and TiO₂).        TiO₂/Fe₂O₃ (substrate: silicon oxide; first layer: TiO₂; second        layer: Fe₂O₃), TiO₂/Berlin blau, TiO₂/Cr₂O₃, or TiO₂/FeTiO₃. In        general the layer thickness ranges from 1 to 1000 nm, preferably        from 1 to 300 nm.

In another particularly preferred embodiment the present inventionrelates to interference pigments containing at least three alternatinglayers of high and low refractive index, such as, for example,TiO₂/SiO₂/TiO₂, (SnO₂)TiO₂/SiO₂/TiO₂, TiO₂/SiO₂/TiO₂/SiO₂TiO₂ orTiO₂/SiO₂/Fe₂O₃: Preferably the layer structure is as follows:

-   -   (A) a coating having a refractive index>1.65,    -   (B) a coating having a refractive index≦1.65,    -   (C) a coating having a refractive index>1.65, and    -   (D) optionally an outer protective layer.

The thickness of the individual layers of high and low refractive indexon the base substrate is essential for the optical properties of thepigment. The thickness of the individual layers, especially metal oxidelayers, depends on the field of use and is generally 10 to 1000 nm,preferably 15 to 800 nm, in particular 20 to 600 nm.

The thickness of layer (A) is 10 to 550 nm, preferably 15 to 400 nm and,in particular, 20 to 350 nm. The thickness of layer (B) is 10 to 1000nm, preferably 20 to 800 nm and, in particular, 30 to 600 nm. Thethickness of layer (C) is 10 to 550 nm, preferably 15 to 400 nm and, inparticular, 20 to 350 nm.

Particularly suitable materials for layer (A) are metal oxides, metalsulfides, or metal oxide mixtures, such as TiO₂, Fe₂O₃, TiFe₂O₅, Fe₃O₄,BiOCl, CoO, Co₃O₄, Cr₂O₃, VO₂, V₂O₃, Sn(Sb)O₂, SnO₂, ZrO₂, irontitanates, iron oxide hydrates, titanium suboxides (reduced titaniumspecies having oxidation states from 2 to ≦4), bismuth vanadate, cobaltaluminate, and also mixtures or mixed phases of these compounds with oneanother or with other metal oxides. Metal sulfide coatings arepreferably selected from sulfides of tin, silver, lanthanum, rare earthmetals, preferably cerium, chromium, molybdenum, tungsten, iron, cobaltand/or nickel.

Particularly suitable materials for layer (B) are metal oxides or thecorresponding oxide hydrates, such as SiO₂, MgF₂, Al₂O₃, AlOOH, B₂O₃ ora mixture thereof, preferably SiO₂.

Particularly suitable materials for layer (C) are colorless or coloredmetal oxides, such as TiO₂, Fe₂O₃, TiFe₂O₅, Fe₃O₄, BiOCl, CoO, Co₃O₄,Cr₂O₃, VO₂, V₂O₃, Sn(Sb)O₂, SnO₂, ZrO₂, iron titanates, iron oxidehydrates, titanium suboxides (reduced titanium species having oxidationstates from 2 to ≦4), bismuth vanadate, cobalt aluminate, and alsomixtures or mixed phases of these compounds with one another or withother metal oxides. The TiO₂ layers can additionally contain anabsorbing material, such as carbon, selectively absorbing colorants,selectively absorbing metal cations, can be coated with absorbingmaterial, or can be partially reduced.

Interlayers of absorbing or nonabsorbing materials can be presentbetween layers (A), (B), (C) and (D). The thickness of the interlayersis 1 to 50 nm, preferably 1 to 40 nm and, in particular, 1 to 30 nm.

In this embodiment preferred interference pigments have the followinglayer structure: SiO_(y) TiO₂ SiO₂ TiO₂ SiO_(y) TiO₂ SiO₂ Fe₂O₃ SiO_(y)TiO₂ SiO₂ TiO₂/Fe₂O₃ SiO_(y) TiO₂ SiO₂ (Sn,Sb)O₂ SiO_(y) (Sn,Sb)O₂ SiO₂TiO₂ SiO_(y) Fe₂O₃ SiO₂ (Sn,Sb)O₂ SiO_(y) TiO₂/Fe₂O₃ SiO₂ TiO₂/Fe₂O₃SiO_(y) TiO₂ SiO₂ MoS₂ SiO_(y) TiO₂ SiO₂ Cr₂O₃ SiO_(y) Cr₂O₃ SiO₂ TiO₂SiO_(y) Fe₂O₃ SiO₂ TiO₂ SiO_(y) TiO₂ Al₂O₃ TiO₂ SiO_(y) Fe₂TiO₅ SiO₂TiO₂ SiO_(y) TiO₂ SiO₂ Fe₂TiO₅/TiO₂ SiO_(y) TiO suboxides SiO₂ TiOsuboxides SiO_(y) TiO₂ SiO₂ TiO₂ + SiO₂ + TiO₂ + Prussian Blue SiO_(y)TiO₂ SiO₂ TiO₂ + SiO₂ + TiO₂ SiO_(y) TiO₂ + SiO₂ + TiO₂ SiO₂ TiO₂ +SiO₂ + TiO₂

The pigments of the present invention are characterized by the preciselydefined thickness and smooth surface of the thin SiO_(y) flakes.

The metal oxide layers can be applied by CVD (chemical vapourdeposition) or by wet chemical coating. The metal oxide layers can beobtained by decomposition of metal carbonyls in the presence of watervapour (relatively low molecular weight metal oxides such as magnetite)or in the presence of oxygen and, where appropriate, water vapour (e.g.nickel oxide and cobalt oxide). The metal oxide layers are especiallyapplied by means of oxidative gaseous phase decomposition of metalcarbonyls (e.g. iron pentacarbonyl, chromium hexacarbonyl; EP-A-45 851),by means of hydrolytic gaseous phase decomposition of metal alcoholates(e.g. titanium and zirconium tetra-n- and -iso-propanolate; DE-A-41 40900) or of metal halides (e.g. titanium tetrachloride; EP-A-338 428), bymeans of oxidative decomposition of organyl tin compounds (especiallyalkyl tin compounds such as tetrabutyltin and tetramethyltin; DE-A-44 03678) or by means of the gaseous phase hydrolysis of organyl siliconcompounds (especially di-tert-butoxyacetoxysilane) described in EP-A-668329, it being possible for the coating operation to be carried out in afluidised-bed reactor (EP-A-045 851 and EP-A-1 06 235). Al₂O₃ layers (B)can advantageously be obtained by controlled oxidation during thecooling of aluminium-coated pigments, which is otherwise carried outunder inert gas (DE-A-195 16 181).

Phosphate-, chromate- and/or vanadate-containing and also phosphate- andSiO₂-containing metal oxide layers can be applied in accordance with thepassivation methods described in DE-A-42 36 332 and in EP-A-678 561 bymeans of hydrolytic or oxidative gaseous phase decomposition ofoxide-halides of the metals (e.g. CrO₂Cl₂, VOCl₃), especially ofphosphorus oxyhalides (e.g. POCl₃), phosphoric and phosphorous acidesters (e.g. di- and tri-methyl and di- and tri-ethyl phosphite) and ofamino-group-containing organyl silicon compounds (e.g.3-aminopropyl-triethoxy- and -trimethoxy-silane).

Layers of oxides of the metals zirconium, titanium, iron and zinc, oxidehydrates of those metals, iron titanates, titanium suboxides or mixturesthereof are preferably applied by precipitation by a wet chemicalmethod, it being possible, where appropriate, for the metal oxides to bereduced. In the case of the wet chemical coating, the wet chemicalcoating methods developed for the production of pearlescent pigments maybe used; these are described, for example, in DE-A-1467468,DE-A-1959988, DE-A-20 09566, DE-A-2214545, DE-A-2215191, DE-A-2244298,DE-A-2313 331, DE-A-25 22572, DE-A-31 37808, DE-A-31 37809, DE-A-31 51343, DE-A-31 51 354, DE-A-31 51 355, DE-A-3211 602 and DE-A-32 35017, DE19599 88, WO 93108237, WO 98(53001 and WO03/6558.

The metal oxide of high refractive index is preferably TiO₂ and/or ironoxide, and the metal oxide of low refractive index is preferably SiO₂.Layers of TiO₂ can be in the rutile or anastase modification, whereinthe rutile modification is preferred. TiO₂ layers can also be reduced byknown means, for example ammonia, hydrogen, hydrocarbon vapor ormixtures thereof, or metal powders, as described in EP-A-735,114,DE-A-3433657, DE-A-4125134, EP-A-332071, EP-A-707,050 or WO93119131.

For the purpose of coating, the substrate particles are suspended inwater and one or more hydrolysable metal salts are added at a pHsuitable for the hydrolysis, which is so selected that the metal oxidesor metal oxide hydrates are precipitated directly onto the particleswithout subsidiary precipitation occurring. The pH is usually keptconstant by simultaneously metering in a base. The pigments are thenseparated off, washed, dried and, where appropriate, calcinated, itbeing possible to optimise the calcinating temperature with respect tothe coating in question. If desired, after individual coatings have beenapplied, the pigments can be separated off, dried and, whereappropriate, calcinated, and then again resuspended for the purpose ofprecipitating further layers.

The metal oxide layers are also obtainable, for example, in analogy to amethod described in DE-A-1 95 01 307, by producing the metal oxide layerby controlled hydrolysis of one or more metal acid esters, whereappropriate in the presence of an organic solvent and a basic catalyst,by means of a sol-gel process. Suitable basic catalysts are, forexample, amines, such as triethylamine, ethylenediamine, tributylamine,dimethylethanolamine and methoxy-propylamine. The organic solvent is awater-miscible organic solvent such as a C₁-alcohol, especiallyisopropanol.

Suitable metal acid esters are selected from alkyl and aryl alcoholates,carboxylates, and carboxyl-radical- or alkyl-radical- oraryl-radical-substituted alkyl alcoholates or carboxylates of vanadium,titanium, zirconium, silicon, aluminium and boron. The use oftriisopropyl aluminate, tetraisopropyl titanate, tetraisopropylzirconate, tetraethyl orthosilicate and triethyl borate is preferred. Inaddition, acetylacetonates and acetoacetylacetonates of theafore-mentioned metals may be used. Preferred examples of that type ofmetal acid ester are zirconium acetylacetonate, aluminiumacetylacetonate, titanium acetylacetonate and diisobutyloleylacetoacetylaluminate or diisopropyloleyl acetoacetylacetonate andmixtures of metal acid esters, for example Dynasil® (Hüls), a mixedaluminium/silicon metal acid ester.

As a metal oxide having a high refractive index, titanium dioxide ispreferably used, the method described in U.S. Pat. No. 3,553,001 beingused, in accordance with an embodiment of the present invention, forapplication of the titanium dioxide layers.

An aqueous titanium salt solution is slowly added to a suspension of thematerial being coated, which suspension has been heated to about 50-100° C., especially 70-80° C., and a substantially constant pH value ofabout from 0.5 to 5, especially about from 1.2 to 2.5, is maintained bysimultaneously metering in a base such as, for example, aqueous ammoniasolution or aqueous alkali metal hydroxide solution. As soon as thedesired layer thickness of precipitated TiO₂ has been achieved, theaddition of titanium salt solution and base is stopped.

This method, also referred to as the “titration method”, isdistinguished by the fact that an excess of titanium salt is avoided.That is achieved by feeding in for hydrolysis, per unit time, only thatamount which is necessary for even coating with the hydrated TiO₂ andwhich can be taken up per unit time by the available surface of theparticles being coated. In principle, the anatase form of TiO₂ forms onthe surface of the starting pigment. By adding small amounts of SnO₂,however, it is possible to force the rutile structure to be formed. Forexample, as described in WO 93(08237, fin dioxide can be depositedbefore titanium dioxide precipitation and the product coated withtitanium dioxide can be calcined at from 800 to 900° C.

The TiO₂ can optionally be reduced by usual procedures: U.S. Pat. No.4,948,631 (NH₃, 750-850° C.), WO93/19131 (H_(2, >900)° C.) orDE-A-19843014 (solid reduction agent, such as, for example,silicon, >600° C.).

Where appropriate, an SiO₂ (protective) layer can be applied on top ofthe titanium dioxide layer, for which the following method may be used:A soda waterglass solution is metered in to a suspension of the materialbeing coated, which suspension has been heated to about 50-100° C.,especially 70-80° C. The pH is maintained at from 4 to 10, preferablyfrom 6.5 to 8.5, by simultaneously adding 10% hydrochloric acid. Afteraddition of the waterglass solution, stirring is carried out for 30minutes.

It is possible to obtain pigments that are more intense in colour andmore transparent by applying, on top of the TiO₂ layer, a metal oxide of“low” refractive index, that is to say a refractive index smaller thanabout 1.65, such as SiO₂, Al₂O₃, AlOOH, B₂O₃ or a mixture thereof,preferably SiO₂, and applying a further Fe₂O₃ and/or TiO₂ layer on topof the latter layer. Such multi-coated interference pigments comprisinga silicon oxide substrate and alternating metal oxide layers of withhigh and low refractive index can be prepared in analogy to theprocesses described in WO98/53011 and WO99/20695.

It is, in addition, possible to modify the powder colour of the pigmentby applying further layers such as, for example, coloured metal oxidesor Berlin Blue, compounds of transition metals, e.g. Fe, Cu, Ni, Co, Cr,or organic compounds such as dyes or colour lakes.

In addition, the pigment according to the invention can also be coatedwith poorly soluble, firmly adhering, inorganic or organic colourants.Preference is given to the use of colour lakes and, especially,aluminium colour lakes. For that purpose an aluminium hydroxide layer isprecipitated, which is, in a second step, laked by using a colour lake(DE-A-24 29 762 and DE 29 28 287).

Furthermore, the pigment according to the invention may also have anadditional coating with complex salt pigments, especially cyanoferratecomplexes (EP-A-141 173 and DE-A-23 13 332).

To enhance the weather and light stability the multiplayer silicon oxideflakes can be, depending on the field of application, subjected to asurface treatment. Useful surface treatments are, for example, describedin DE-A-2215191, DE-A-3151354, DE-A-3235017, DE-A-3334598, DE-A-4030727,EP-A-649886, WO97/29059, WO99/57204, and US-A-5,759,255. Said surfacetreatment might also facilitate the handling of the pigment, especiallyits incorporation into various application media.

The SiO_(y) flakes are prepared by a process comprising the steps(WO03/68868):

-   -   a) vapour-deposition of a separating agent onto a (movable)        carrier to produce a separating agent layer,    -   b) vapour-deposition of an SiO_(y) layer onto the separating        agent layer, wherein 0.70≦y≦1.8,    -   c) dissolution of the separating agent layer in a solvent, and    -   d) separation of the SiO_(y) from the solvent.

SiO_(y) with y>1.0 can be obtained by evaporation of SiO in the presenceof oxygen. Layers, which are essentially free of absorption, can beobtained, if the growing SiO_(y) layer is irradiated with UV lightduring evaporation (DE-A-1621214). It is possible to obtain SiO_(1.5)layers, which do not absorb in the visible region and have a refractiveindex of 1.55 at 550 nm, by so-called “reactive evaporation” of SiO in apure oxygen atmosphere (E. Ritter, J. Vac. Sci. Technol. 3 (1966) 225).

The SiO_(y) layer in step b) being vapour-deposited from a vaporisercontaining a charge comprising a mixture of Si and SiO₂, SiO_(y) or amixture thereof, the weight ratio of Si to SiO₂ being preferably in therange from 0.15:1 to 0.75:1, and especially containing a stoichiometricmixture of Si and SiO₂ or a vaporiser containing a charge comprisingsilicon monoxide containing silicon in an amount up to 20% by weight(0.70≦y<1.0). Step c) being advantageously carried out at a pressurethat is higher than the pressure in steps a) and b) and lower thanatmospheric pressure. The SiO_(y) flakes obtainable by this method havea thickness in the range preferably from 20 to 2000 nm, especially from20 to 500 nm, most preferred from 50 to 350 nm, the ratio of thethickness to the surface area of the plane-parallel structures beingpreferably less than 0.01 μm-1. The plane-parallel structures therebyproduced are distinguished by high uniformity of thickness, a superiorplanarity and smoothness (surface microstructure).

The silicon oxide layer in step b) is formed preferably from siliconmonoxide vapour produced in the vaporiser by reaction of a mixture of Siand SiO₂ at temperatures of more than 1300° C.

The vapour-deposition in steps a) and b) is carried out preferably undera vacuum of <0.5 Pa. The dissolution of the separating agent layer instep c) is carried out at a pressure in the range preferably from 1 to5×10⁴ Pa, especially from 600 to 10⁴ Pa, and more especially from 10³ to5×10³ Pa.

The separating agent vapour-deposited onto the carrier in step a) may bea lacquer (coating), a polymer, such as, for example, the(thermoplastic) polymers, in particular acryl- or styrene polymers ormixtures thereof, as described in U.S. Pat. No. 6,398,999, an organicsubstance soluble in organic solvents or water and vaporisable in vacuo,such as anthracene, anthraquinone, acetamidophenol, acetylsalicylicacid, camphoric anhydride, benzimidazole, benzene-1,2,4-tricarboxylicacid, biphenyl-2,2-dicarboxylic acid, bis(4-hydroxyphenyl)sulfone,dihydroxyanthraquinone, hydantoin, 3-hydroxybenzoic acid,8-hydroxyquinoline-5-sulfonic acid monohydrate, 4-hydroxycoumarin,7-hydroxycoumarin, 3-hydroxynaphthalene-2-carboxylic acid, isophthalicacid, 4,4-methylene-bis-3-hydroxy-naphthalene-2-carboxylic acid,naphthalene-1,8-dicarboxylic anhydride, phthalimide and its potassiumsalt, phenolphthalein, phenothiazine, saccharin and its salts,tetraphenylmethane, triphenylene, triphenylmethanol or a mixture of atleast two of those substances. The separating agent is preferably aninorganic salt soluble in water and vaporisable in vacuo (see, forexample, DE 19844357), such as sodium chloride, potassium chloride,lithium chloride, sodium fluoride, potassium fluoride, lithium fluoride,calcium fluoride, sodium aluminium fluoride and disodium tetraborate.

The movable carrier may consist of one or more discs, cylinders or otherrotationally symmetrical bodies, which rotate about an axis (cf.WO01/25500), and consists preferably of one or more continuous metalbelts with or without a polymeric coating or of one or more polyimide orpolyethylene terephthalate belts (U.S. Pat. No. 6,270,840).

Step d) may comprise washing-out and subsequent filtration,sedimentation, centrifugation, decanting and/or evaporation. Theplane-parallel structures of SiO_(y) may, however, also be frozentogether with the solvent in step d) and subsequently subjected to aprocess of freeze-drying, whereupon the solvent is separated off as aresult of sublimation below the triple point and the dry SiO_(y) remainsbehind in the form of individual plane-parallel structures.

The invention relates also to plane-parallel structures of SiO_(y) thatare obtainable by this method and have a thickness preferably in therange from 20 to 2000 nm, especially 20 to 500 nm, most preferred 50 to350 nm.

Except under an ultra-high vacuum, in technical vacuums of a few 10⁻² Pavaporised SiO always condenses as SiO_(y) wherein 1≦y≦1.8, especiallywherein 1.1≦y≦1.8, because high-vacuum apparatuses always contain, as aresult of gas emission from surfaces, traces of water vapour which reactwith the readily reactive SiO at vaporisation temperature.

On its further course, the belt-form carrier, which is closed to form aloop, runs through dynamic vacuum lock chambers of known mode ofconstruction (cf. U.S. Pat. No. 6,270,840) into a region of from 1 to5×10⁴ Pa pressure, preferably from 600 to 10⁴ Pa pressure, andespecially from 10³ to 5×10³ Pa pressure, where it is immersed in adissolution bath. The temperature of the solvent should be so selectedthat its vapour pressure is in the indicated pressure range. Withmechanical assistance, the separating agent layer rapidly dissolves andthe product layer breaks up into flakes, which are then present in thesolvent in the form of a suspension. On its further course, the belt isdried and freed from any contaminants still adhering to it. It runsthrough a second group of dynamic vacuum lock chambers back into thevaporisation chamber, where the process of coating with separating agentand product layer of SiO is repeated.

The suspension then present in both cases, comprising product structuresand solvent, and the separating agent dissolved therein, is thenseparated in a further operation in accordance with a known technique.For that purpose, the product structures are first concentrated in theliquid and rinsed several times with fresh solvent in order to wash outthe dissolved separating agent. The product, in the form of a solid thatis still wet, is then separated off by filtration, sedimentation,centrifugation, decanting or evaporation.

The product can then be brought to the desired particle size by means ofultrasound or by mechanical means using high-speed stirrers in a liquidmedium, or after drying the fragments in an air-jet mill having a rotaryclassifier, or means of grinding or air-sieving and delivered forfurther use.

In the production of the silicon/silicon oxide flakes, variants arepossible:

It is possible to arrange several separating agent and productvaporisers one after the other in the running direction of the belt inthe vaporisation zone. By that means there is obtained, with littleadditional outlay in terms of apparatus, a layer sequence of S+P+S+P,wherein S is the separating agent layer and P is the product layer. Ifthe number of vaporisers is doubled and the belt speed is the same,twice the amount of product is obtained.

Separating off the plane-parallel structures after washing-out atatmospheric pressure can be carried out under gentle conditions byfreezing the suspension, which has been concentrated to a solids contentof about 50%, and subjecting it in known manner to freeze-drying atabout −10° C. and 50 Pa pressure. The dry substance remains behind asproduct, which can be subjected to the steps of further processing bymeans of coating or chemical conversion.

Instead of using a continuous belt, it is possible to produce theproduct by carrying out the steps of vapour-deposition of separatingagent and SiO, of dissolution, and of drying the carrier, in anapparatus having a rotary body, in accordance with WO01/25500. Therotary body may be one or more discs, a cylinder or any otherrotationally symmetrical body.

The SiO_(y) flakes may be oxidised using an oxygen-containing gas suchas, for example, air at a temperature of at least 200° C., especially atabove 400° C., preferably in the form of loose material, in a fluidisedbed or by introduction into an oxidising flame, preferably at atemperature in the range from 500 to 1000° C., to form plane-parallelstructures of SiO_(y) (WO03/068868).

At present, it can not be excluded, that by heating TiO₂/SiO_(y)particles at a temperature above 400° C., especially 400 to 1100° C.,reduction of TiO₂ by SiO_(y)TiO₂+SiO_(y)→SiO_(y+b)+TiO₂.and/or disproportionation of SiO_(y) in SiO₂ and Si occurs.SiO_(y)→(y/y+a)SiO_(y+a)+(1−(y/y+a)) Si

In this disproportion SiO_(y+a) flakes are formed, containing(1−(y/y+a)) Si, wherein 0.03≦y≦1.95, especially 0.70≦y≦0.99 or 1≦y≦1.8,0.05≦a≦1.97, especially 0.05≦a≦1.30, and the sum y and a is equal orless than 2. SiO_(y+a) is an oxygen enriched silicon suboxide.

The flakes of the present invention are not of a uniform shape.Nevertheless, for purposes of brevity, the flakes will be referred to ashaving a “diameter.” The SiO_(y) flakes have a high plane-parallelismand a defined thickness in the range of ±10%, especially ±5% of theaverage thickness. The SiO_(y) flakes have a thickness of from 20 to2000 nm, especially from 20 to 500 nm, most preferred 50 to 350 nm. Itis presently preferred that the diameter of the flakes be in a preferredrange of about 1-60 μm with a more preferred range of about 5-40 μm.Thus, the aspect ratio of the flakes of the present invention is in apreferred range of about 2 to 3000 with a more preferred range of about14 to 800. If a TiO₂ layer is deposited as a material of high refractiveindex, the TiO₂ layer has a thickness of 20 to 200 nm, especially 20 to100 nm, and more especially 20 to 50 nm. Due to the smaller thicknessdistribution of the SiO_(y) flakes as compared to commercially availableSiO₂ flakes effect pigments having a higher color purity result.

If the SiO_(y) substrates of the present invention are used instead ofmica flakes or SiO₂ substrates obtained according to the processdescribed in WO93108237, interference pigments having superiorbrilliance, clear and intense colors, intense color flop, improved colorstrength and color purity can be obtained.

In another preferred embodiment of the present invention the SiO_(y)flakes have a thickness of from 20 to 200 nm, especially from 40 to 150nm, most preferred 60 to 120 nm. The SiO_(y) flakes have a highplane-parallelism and a defined thickness in the range of ±30%,especially ±10% of the average thickness. It is presently preferred thatthe diameter of the flakes be in a preferred range of about 1 to 60 μm,especially 2 to 50 μm, with a more preferred range of about 5-40 μm.Thus, the aspect ratio of the flakes of the present invention is in apreferred range of about 4 to 1250 with a more preferred range of about42 to 670. If a TiO₂ layer is deposited as a material of high refractiveindex, the TiO₂ layer has a thickness of 20 to 200 nm, especially 50 to200 nm. The total thickness of the TiO₂-coated SiO_(y) flakes isespecially 150 to 450 nm. Starting, for example, from SiO_(y) flakes(y=1.4 to 1.8) having a thickness of 90±30% it is possible to obtain red(ca. 73 nm), green (ca. 150 nm), or blue (ca. 130 nm) interferencepigments by selecting the thickness of the TiO₂ layer. Due to the smallthickness distribution of the SiO_(y) flakes effect pigments resulthaving a high color purity. The SiO_(y) flakes may be oxidised using anoxygen-containing gas such as, for example, air at a temperature of atleast 200° C., especially at above 400° C., preferably in the form ofloose material, in a fluidised bed or by introduction into an oxidisingflame, preferably at a temperature in the range from 500 to 1000° C., toform plane-parallel structures of SiO₂ (WO031068868). Alternatively, theSiO_(y) flakes can be heated in an oxygen-free atmosphere such as, forexample, argon and/or helium or under a vacuum of less than 13 Pa (10⁻¹Torr) at a temperature of at least 400° C., especially at above 400° C.,preferably in the form of loose material, in a fluidised bed, preferablyat a temperature in the range from 900 to 1100° C., to form thesilicon/silicon oxide flakes. Both the SiO₂ flakes as well as thesilicon/silicon oxide flakes can be used instead of the SiO_(y) flakesas substrate for effect pigments.

Metallic or non-metallic, inorganic platelet-shaped particles orpigments are effect pigments, (especially metal effect pigments orinterference pigments), that is to say, pigments that, besides impartingcolour to an application medium, impart additional properties, forexample angle dependency of the colour (flop), lustre (not surfacegloss) or texture. On metal effect pigments, substantially orientedreflection occurs at directionally oriented pigment particles.

In the case of interference pigments, the colour-imparting effect is dueto the phenomenon of interference of light in thin, highly refractivelayers.

The (effect) pigments according to the invention can be used for allcustomary purposes, for example for colouring polymers in the mass,coatings (including effect finishes, including those for the automotivesector) and printing inks (including offset printing, intaglio printing,bronzing and flexographic printing), and also, for example, forapplications in cosmetics, in ink-jet printing, for dyeing textiles,glazes for ceramics and glass as well as laser marking of papers andplastics. Such applications are known from reference works, for example“Industrielle Organische Pigmente” (W. Herbst and K. Hunger, VCHVerlagsgesellschaft mbH, WeinheimlNew York, 2nd, completely revisededition, 1995).

When the pigments according to the invention are interference pigments(effect pigments), they are goniochromatic and result in brilliant,highly saturated (lustrous) colours. They are accordingly veryespecially suitable for combination with conventional, transparentpigments, for example organic pigments such as, for example,diketopyrrolopyrroles, quinacridones, dioxazines, perylenes,isoindolinones etc., it being possible for the transparent pigment tohave a similar colour to the effect pigment. Especially interestingcombination effects are obtained, however, in analogy to, for example,EP-A-388 932 or EP-A-402 943, when the colour of the transparent pigmentand that of the effect pigment are complementary. The pigments accordingto the invention can be used with excellent results for pigmenting highmolecular weight organic material.

The high molecular weight organic material for the pigmenting of whichthe pigments or pigment compositions according to the invention may beused may be of natural or synthetic origin. High molecular weightorganic materials usually have molecular weights of about from 10³ to10⁸ g/mol or even more. They may be, for example, natural resins, dryingoils, rubber or casein, or natural substances derived therefrom, such aschlorinated rubber, oil-modified alkyd resins, viscose, cellulose ethersor esters, such as ethylcellulose, cellulose acetate, cellulosepropionate, cellulose acetobutyrate or nitrocellulose, but especiallytotally synthetic organic polymers (thermosetting plastics andthermoplastics), as are obtained by polymerisation, polycondensation orpolyaddition. From the class of the polymerisation resins there may bementioned, especially, polyolefins, such as polyethylene, polypropyleneor polyisobutylene, and also substituted polyolefins, such aspolymerisation products of vinyl chloride, vinyl acetate, styrene,acrylonitrile, acrylic acid esters, methacrylic acid esters orbutadiene, and also copolymerisation products of the said monomers, suchas especially ABS or EVA.

From the series of the polyaddition resins and polycondensation resinsthere may be mentioned, for example, condensation products offormaldehyde with phenols, so-called phenoplasts, and condensationproducts of formaldehyde with urea, thiourea or melamine, so-calledaminoplasts, and the polyesters used as surface-coating resins, eithersaturated, such as alkyd resins, or unsaturated, such as maleate resins;also linear polyesters and polyamides, polyurethanes or silicones.

The said high molecular weight compounds may be present singly or inmixtures, in the form of plastic masses or melts. They may also bepresent in the form of their monomers or in the polymerised state indissolved form as film-formers or binders for coatings or printing inks,such as, for example, boiled linseed oil, nitrocellulose, alkyd resins,melamine resins and urea-formaldehyde resins or acrylic resins.

Depending on the intended purpose, it has proved advantageous to use theeffect pigments or effect pigment compositions according to theinvention as toners or in the form of preparations. Depending on theconditioning method or intended application, it may be advantageous toadd certain amounts of texture-improving agents to the effect pigmentbefore or after the conditioning process, provided that this has noadverse effect on use of the effect pigments for colouring highmolecular weight organic materials, especially polyethylene. Suitableagents are, especially, fatty acids containing at least 18 carbon atoms,for example stearic or behenic acid, or amides or metal salts thereof,especially magnesium salts, and also plasticisers, waxes, resin acids,such as abietic acid, rosin soap, alkylphenols or aliphatic alcohols,such as stearyl alcohol, or aliphatic 1,2-dihydroxy compounds containingfrom 8 to 22 carbon atoms, such as 1,2-dodecanediol, and also modifiedcolophonium maleate resins or fumaric acid colophonium resins. Thetexture-improving agents are added in amounts of preferably from 0.1 to30% by weight, especially from 2 to 15% by weight, based on the endproduct.

The (effect) pigments according to the invention can be added in anytinctorially effective amount to the high molecular weight organicmaterial being pigmented. A pigmented substance composition comprising ahigh molecular weight organic material and from 0.01 to 80% by weight,preferably from 0.1 to 30% by weight, based on the high molecular weightorganic material, of an pigment according to the invention isadvantageous. Concentrations of from 1 to 20% by weight, especially ofabout 10% by weight, can often be used in practice.

High concentrations, for example those above 30% by weight, are usuallyin the form of concentrates (“masterbatches”) which can be used ascolorants for producing pigmented materials having a relatively lowpigment content, the pigments according to the invention having anextraordinarily low viscosity in customary formulations so that they canstill be processed well.

For the purpose of pigmenting organic materials, the effect pigmentsaccording to the invention may be used singly. It is, however, alsopossible, in order to achieve different hues or colour effects, to addany desired amounts of other colour-imparting constituents, such aswhite, coloured, black or effect pigments, to the high molecular weightorganic substances in addition to the effect pigments according to theinvention. When coloured pigments are used in admixture with the effectpigments according to the invention, the total amount is preferably from0.1 to 10% by weight, based on the high molecular weight organicmaterial. Especially high goniochromicity is provided by the preferredcombination of an effect pigment according to the invention with acoloured pigment of another colour, especially of a complementarycolour, with colorations made using the effect pigment and colorationsmade using the coloured pigment having, at a measurement angle of 10°, adifference in hue (AH*) of from 20 to 340, especially from 150 to 210.

Preferably, the effect pigments according to the invention are combinedwith transparent coloured pigments, it being possible for thetransparent coloured pigments to be present either in the same medium asthe effect pigments according to the invention or in a neighbouringmedium. An example of an arrangement in which the effect pigment and thecoloured pigment are advantageously present in neighbouring media is amulti-layer effect coating.

The pigmenting of high molecular weight organic substances with thepigments according to the invention is carried out, for example, byadmixing such a pigment, where appropriate in the form of a masterbatch,with the substrates using roll mills or mixing or grinding apparatuses.The pigmented material is then brought into the desired final form usingmethods known per se, such as calendering, compression moulding,extrusion, coating, pouring or injection moulding. Any additivescustomary in the plastics industry, such as plasticisers, fillers orstabilisers, can be added to the polymer, in customary amounts, beforeor after incorporation of the pigment. In particular, in order toproduce non-rigid shaped articles or to reduce their brittleness, it isdesirable to add plasticisers, for example esters of phosphoric acid,phthalic acid or sebacic acid, to the high molecular weight compoundsprior to shaping.

For pigmenting coatings and printing inks, the high molecular weightorganic materials and the effect pigments according to the invention,where appropriate together with customary additives such as, forexample, fillers, other pigments, siccatives or plasticisers, are finelydispersed or dissolved in the same organic solvent or solvent mixture,it being possible for the individual components to be dissolved ordispersed separately or for a number of components to be dissolved ordispersed together, and only thereafter for all the components to bebrought together.

Dispersing an effect pigment according to the invention in the highmolecular weight organic material being pigmented, and processing apigment composition according to the invention, are preferably carriedout subject to conditions under which only relatively weak shear forcesoccur so that the effect pigment is not broken up into smaller portions.Plastics comprising the pigment of the invention in amounts of 0.1 to50% by weight, in particular 0.5 to 7% by weight. In the coating sector,the pigments of the invention are employed in amounts of 0.1 to 10% byweight. In the pigmentation of binder systems, for example for paintsand printing inks for intaglio, offset or screen printing, the pigmentis incorporated into the printing ink in amounts of 0.1 to 50% byweight, preferably 5 to 30% by weight and in particular 8 to 15% byweight.

The colorations obtained, for example in plastics, coatings or printinginks, especially in coatings or printing inks, more especially incoatings, are distinguished by excellent properties, especially byextremely high saturation, outstanding fastness properties, high colorpurity and high goniochromicity.

When the high molecular weight material being pigmented is a coating, itis especially a speciality coating, very especially an automotivefinish. The effect pigments according to the invention are also suitablefor making-up the lips or the skin and for colouring the hair or thenails.

The invention accordingly relates also to a cosmetic preparation orformulation comprising from 0.0001 to 90% by weight of a pigment,especially an effect pigment, according to the invention and from 10 to99.9999% of a cosmetically suitable carrier material, based on the totalweight of the cosmetic preparation or formulation.

Such cosmetic preparations or formulations are, for example, lipsticks,blushers, foundations, nail varnishes and hair shampoos.

The pigments may be used singly or in the form of mixtures. It is, inaddition, possible to use pigments according to the invention togetherwith other pigments and/or colorants, for example in combinations asdescribed hereinbefore or as known in cosmetic preparations.

The cosmetic preparations and formulations according to the inventionpreferably contain the pigment according to the invention in an amountfrom 0.005 to 50% by weight, based on the total weight of thepreparation.

Suitable carrier materials for the cosmetic preparations andformulations according to the invention include the customary materialsused in such compositions.

The cosmetic preparations and formulations according to the inventionmay be in the form of, for example, sticks, ointments, creams,emulsions, suspensions, dispersions, powders or solutions. They are, forexample, lipsticks, mascara preparations, blushers, eye-shadows,foundations, eyeliners, powder or nail varnishes.

If the preparations are in the form of sticks, for example lipsticks,eye-shadows, blushers or foundations, the preparations consist for aconsiderable part of fatty components, which may consist of one or morewaxes, for example ozokerite, lanolin, lanolin alcohol, hydrogenatedlanolin, acetylated lanolin, lanolin wax, beeswax, candelilla wax,microcrystalline wax, carnauba wax, cetyl alcohol, stearyl alcohol,cocoa butter, lanolin fatty acids, petrolatum, petroleum jelly, mono-,di- or tri-glycerides or fatty esters thereof that are solid at 25° C.,silicone waxes, such as methyloctadecane-oxypolysiloxane andpoly(dimethylsiloxy)-stearoxysiloxane, stearic acid monoethanolamine,colophane and derivatives thereof, such as glycol abietates and glycerolabietates, hydrogenated oils that are solid at 25° C., sugar glyceridesand oleates, myristates, lanolates, stearates and dihydroxystearates ofcalcium, magnesium, zirconium and aluminium.

The fatty component may also consist of a mixture of at least one waxand at least one oil, in which case the following oils, for example, aresuitable: paraffin oil, purcelline oil, perhydrosqualene, sweet almondoil, avocado oil, calophyllum oil, castor oil, sesame oil, jojoba oil,mineral oils having a boiling point of about from 310 to 410° C.,silicone oils, such as dimethylpolysiloxane, linoleyl alcohol, linolenylalcohol, oleyl alcohol, cereal grain oils, such as wheatgerm oil,isopropyl lanolate, isopropyl palmitate, isopropyl myristate, butylmyristate, cetyl myristate, hexadecyl stearate, butyl stearate, decyloleate, acetyl glycerides, octanoates and decanoates of alcohols andpolyalcohols, for example of glycol and glycerol, ricinoleates ofalcohols and polyalcohols, for example of cetyl alcohol, isostearylalcohol, isocetyl lanolate, isopropyl adipate, hexyl laurate and octyldodecanol.

The fatty components in such preparations in the form of sticks maygenerally constitute up to 99.91% by weight of the total weight of thepreparation.

The cosmetic preparations and formulations according to the inventionmay additionally comprise further constituents, such as, for example,glycols, polyethylene glycols, polypropylene glycols, monoalkanolamides,non-coloured polymeric, inorganic or organic fillers, preservatives, UVfilters or other adjuvants and additives customary in cosmetics, forexample a natural or synthetic or partially synthetic di- ortri-glyceride, a mineral oil, a silicone oil, a wax, a fatty alcohol, aGuerbet alcohol or ester thereof, a lipophilic functional cosmeticactive ingredient, including sun-protection filters, or a mixture ofsuch substances.

A lipophilic functional cosmetic active ingredient suitable for skincosmetics, an active ingredient composition or an active ingredientextract is an ingredient or a mixture of ingredients that is approvedfor dermal or topical application. The following may be mentioned by wayof example:

-   -   active ingredients having a cleansing action on the skin surface        and the hair; these include all substances that serve to cleanse        the skin, such as oils, soaps, synthetic detergents and solid        substances;    -   active ingredients having a deodorising and        perspiration-inhibiting action: they include antiperspirants        based on aluminium salts or zinc salts, deodorants comprising        bactericidal or bacteriostatic deodorising substances, for        example triclosan, hexachlorophene, alcohols and cationic        substances, such as, for example, quaternary ammonium salts, and        odour absorbers, for example OGrillocin (combination of zinc        ricinoleate and various additives) or triethyl citrate        (optionally in combination with an antioxidant, such as, for        example, butyl hydroxytoluene) or ion-exchange resins;    -   active ingredients that offer protection against sunlight (UV        filters): suitable active ingredients are filter substances        (sunscreens) that are able to absorb UV radiation from sunlight        and convert it into heat; depending on the desired action, the        following light-protection agents are preferred:        light-protection agents that selectively absorb sunburn-causing        high-energy UV radiation in the range of approximately from 280        to 315 nm (UV-B absorbers) and transmit the longer-wavelength        range of, for example, from 315 to 400 nm (UV-A range), as well        as light-protection agents that absorb only the        longer-wavelength radiation of the UV-A range of from 315 to 400        nm (UV-A absorbers); suitable light-protection agents are, for        example, organic UV absorbers from the class of the        p-aminobenzoic acid derivatives, salicylic acid derivatives,        benzophenone derivatives, dibenzoylmethane derivatives, diphenyl        acrylate derivatives, benzofuran derivatives, polymeric UV        absorbers comprising one or more organosilicon radicals,        cinnamic acid derivatives, camphor derivatives,        trianilino-s-triazine derivatives, phenyl-benzimidazolesulfonic        acid and salts thereof, menthyl anthranilates, benzotriazole        derivatives, and/or an inorganic micropigment selected from        aluminium oxide- or silicon dioxide-coated TiO₂, zinc oxide or        mica;    -   active ingredients against insects (repellents) are agents that        are intended to prevent insects from touching the skin and        becoming active there; they drive insects away and evaporate        slowly; the most frequently used repellent is diethyl toluamide        (DEET); other common repellents will be found, for example, in        “Pflegekosmetiku (W. Raab and U. Kindl, Gustav-Fischer-Verlag        Stuttgart/New York, 1991) on page 161;    -   active ingredients for protection against chemical and        mechanical influences: these include all substances that form a        barrier between the skin and external harmful substances, such        as, for example, paraffin oils, silicone oils, vegetable oils,        PCL products and lanolin for protection against aqueous        solutions, film-forming agents, such as sodium alginate,        triethanolamine alginate, polyacrylates, polyvinyl alcohol or        cellulose ethers for protection against the effect of organic        solvents, or substances based on mineral oils, vegetable oils or        silicone oils as Olubricants” for protection against severe        mechanical stresses on the skin;    -   moisturising substances: the following substances, for example,        are used as moisture-controlling agents (moisturisers): sodium        lactate, urea, alcohols, sorbitol, glycerol, propylene glycol,        collagen, elastin and hyaluronic acid;    -   active ingredients having a keratoplastic effect: benzoyl        peroxide, retinoic acid, colloidal sulfur and resorcinol;    -   antimicrobial agents, such as, for example, triclosan or        quaternary ammonium compounds;    -   oily or oil-soluble vitamins or vitamin derivatives that can be        applied dermally: for example vitamin A (retinol in the form of        the free acid or derivatives thereof), panthenol, pantothenic        acid, folic acid, and combinations thereof, vitamin E        (tocopherol), vitamin F; essential fatty acids; or niacinamide        (nicotinic acid amide);    -   vitamin-based placenta extracts: active ingredient compositions        comprising especially vitamins A, C, E, B₁, B₂, B₆, B₁₂, folic        acid and biotin, amino acids and enzymes as well as compounds of        the trace elements magnesium, silicon, phosphorus, calcium,        manganese, iron or copper;    -   skin repair complexes: obtainable from inactivated and        disintegrated cultures of bacteria of the bifidus group;    -   plants and plant extracts: for example arnica, aloe, beard        lichen, ivy, stinging nettle, ginseng, henna, camomile,        marigold, rosemary, sage, horsetail or thyme;    -   animal extracts: for example royal jelly, propolis, proteins or        thymus extracts;    -   cosmetic oils that can be applied dermally: neutral oils of the        Miglyol 812 type, apricot kernel oil, avocado oil, babassu oil,        cottonseed oil, borage oil, thistle oil, groundnut oil,        gamma-oryzanol, rosehip-seed oil, hemp oil, hazelnut oil,        blackcurrant-seed oil, jojoba oil, cherry-stone oil, salmon oil,        linseed oil, comseed oil, macadamia nut oil, almond oil, evening        primrose oil, mink oil, olive oil, pecan nut oil, peach kernel        oil, pistachio nut oil, rape oil, rice-seed oil, castor oil,        safflower oil, sesame oil, soybean oil, sunflower oil, tea tree        oil, grapeseed oil or wheatgerm oil.

The preparations in stick form are preferably anhydrous but may incertain cases comprise a certain amount of water which, however, ingeneral does not exceed 40% by weight, based on the total weight of thecosmetic preparation.

If the cosmetic preparations and formulations according to the inventionare in the form of semi-solid products, that is to say in the form ofointments or creams, they may likewise be anhydrous or aqueous. Suchpreparations and formulations are, for example, mascaras, eyeliners,foundations, blushers, eye-shadows, or compositions for treating ringsunder the eyes.

If, on the other hand, such ointments or creams are aqueous, they areespecially emulsions of the water-inoil type or of the oil-in-water typethat comprise, apart from the pigment, from 1 to 98.8% by weight of thefatty phase, from 1 to 98.8% by weight of the aqueous phase and from 0.2to 30% by weight of an emulsifier.

Such ointments and creams may also comprise further conventionaladditives, such as, for example, perfumes, antioxidants, preservatives,gel-forming agents, UV filters, colorants, pigments, pearlescent agents,non-coloured polymers as well as inorganic or organic fillers. If thepreparations are in the form of a powder, they consist substantially ofa mineral or inorganic or organic filler such as, for example, talcum,kaolin, starch, polyethylene powder or polyamide powder, as well asadjuvants such as binders, colorants etc.

Such preparations may likewise comprise various adjuvants conventionallyemployed in cosmetics, such as fragrances, antioxidants, preservativesetc.

If the cosmetic preparations and formulations according to the inventionare nail varnishes, they consist essentially of nitrocellulose and anatural or synthetic polymer in the form of a solution in a solventsystem, it being possible for the solution to comprise other adjuvants,for example pearlescent agents.

In that embodiment, the coloured polymer is present in an amount ofapproximately from 0.1 to 5% by weight.

The cosmetic preparations and formulations according to the inventionmay also be used for colouring the hair, in which case they are used inthe form of shampoos, creams or gels that are composed of the basesubstances conventionally employed in the cosmetics industry and apigment according to the invention.

The cosmetic preparations and formulations according to the inventionare prepared in conventional manner, for example by mixing or stirringthe components together, optionally with heating so that the mixturesmelt.

The Examples that follow illustrate the invention without limiting thescope thereof. Unless otherwise indicated, percentages and parts arepercentages and parts by weight, respectively.

EXAMPLES Example 1

In a vacuum system which in its fundamental points is constructedanalogously to the system described in U.S. Pat. No. 6,270,840, thefollowing are vaporised, from vaporisers, in succession: sodium chloride(NaCl) as separating agent at about 900° C., and silicon monoxide (SiO)as reaction product of Si and SiO₂ at from 1350 to 1550° C. The layerthickness of NaCl is typically 30-50 nm, that of SiO_(y) being,depending on the intended purpose of the end product, from 100 to 2000nm, in the present case 200 nm. Vaporisation is carried out at about0.02 Pa, amounting to about 11 g of NaCl and 72 g of SiO per minute. Forsubsequently detaching the layers by dissolution of the separatingagent, the carrier on which vapour-deposition has taken place is sprayedat about 3000 Pa with deionised water and treated with mechanicalassistance using scrapers and with ultrasound. The NaCl dissolves andthe SiO_(y) layer, which is insoluble, breaks up into flakes. Thesuspension is continuously removed from the dissolution chamber and, atatmospheric pressure, is concentrated by filtration and rinsed severaltimes with deionised water in order to remove Na⁺ and Cl⁻ ions that arepresent. That is followed by the steps of drying and heating theplane-parallel SiO_(y) structures in the form of loose material at 500to 600° C. for two hours in an oven through which air heated to 500 to600° C. is passed. After cooling, comminution and grading by air-sievingare carried out.

Belspiel 2

Two Layer System

1) TiO₂ Layer:

100 g of the SiO_(y) flakes obtained in example 1 are suspended in 1,5 Ifully deionized water and heated to 75° C. To this suspension 160 ml ofan aqueous solution of TiCl₄ (400 g TiCl₄/l) is metered within 90minutes. The pH is kept constant at pH=2.2 by means of 32% sodiumhydroxide solution. After this solution has been added, the mixture isstirred for a further approximately 30 minutes at 75° C.

2) SiO Layer:

The pH of the suspension is increased by means of sodium hydroxidesolution to 7,5 and within 3.5 hours 720 ml a sodium water glasssolution is metered (125 g SiO₂/l) at 75° C. During the addition the pHis kept constant by means of 10% hydrochloric acid. After this solutionhas been added, the mixture is stirred for a further 30 minutes at 75°C. The thus obtained pigment is characterized intense blue interferencecolor.

Example 3

3 Layer System comprising a Fe₂O₃ Layer

1) TiO₂ Layer

The TiO₂ layer is obtained as described in Example 1.

2) SiO₂ Layer:

The SiO₂ layer is obtained as described in Example 1.

3) Fe₂O₃ Layer:

The pH of the suspension of the silicon oxide flakes coated succesivelywith TiO₂ and SiO₂ is controlled by means of 10% hydrochloric acid to3.0. Then 1750 ml of an aqueous FeCl₃-Lösung (35 g Fe/l) are added at75° C. within 5 h. The pH is kept constant by simultaneously adding 32%NaOH. After this solution has been added, the mixture is stirred for afurther approximately 45 minutes at 75° C. After the suspension hascooled to room temperature, the product is filtered, washed saltfreewith water and dried at 110° C. Then the pigment is calcinated 30minutes at 850° C.

Example 4

250 mg of 295 nm thick SiO_(y) (y˜1.7-1.8) flakes (average diameter ˜50microns), which have a green color on a black background, are mixed in35 ml deionized water and then heated to 60° C. The pH is adjusted to1.4 with 1N hydrochloric acid. 10 ml of TiOCl₂ (diluted with 1N HCl,such that the solution comprises 1.5% of titanium) are added to thesolution during 5 hours, while maintaining the pH at 1.4 by continuousaddition of sodium hydroxide. The liquid is cooled to room temperatureand filtered with a 20 micron sieve. The obtained powder is dried for 1hour at 60° C. in air. White looking flakes are obtained which have abright blue color when viewed on a black background. The color dependson the observation angle and turns violet and then yellow whenincreasing the viewing angle.

1. A pigment comprising particles having a length of from 2 μm to 5 mm,a width of from 2 μm to 2 mm, and a thickness of from 20 nm to 2 μm, anda ratio of length to thickness of at least 2:1, wherein the particlescontain a core of SiO_(y) with 0.70≦y≦1.95, having two substantiallyparallel faces, the distance between which is the shortest axis of thecore, and (a) a material having a high index of refraction.
 2. A pigmentcomprising particles having a length of from 2 μm to 5 mm, a width offrom 2 μm to 2 mm, and a thickness of from 20 nm to 2 μm, and a ratio oflength to thickness of at least 2:1, wherein the particles contain acore of SiO_(y) with 0.70≦y≦1.95, having two substantially parallelfaces, the distance between which is the shortest axis of the core, and(a) a thin semi-transparent metal layer.
 3. The pigment according toclaim 1, wherein the pigment comprises in addition (b) a metal oxide oflow refractive index, wherein the difference of the refractive indicesis at least 0,
 1. 4. The pigment according to claim 1, wherein the metaloxide of high refractive index is one or more compounds selected fromthe group consisting of TiO₂, ZrO₂, Fe₂O₃, Fe₃O₄, Cr₂O₃, ZnO, an irontitanate, an iron oxide hydrate and a titanium suboxide or a mixed phaseof these compounds.
 5. The pigment according to claim 3, wherein themetal oxide of low index of refraction is one or more compounds selectedfrom the group consisting of SiO₂, Al₂O₃, AlOOH and B₂O₃, wherein alkalior earth alkali metal oxides can be contained as additional component.6. The pigment according to claim 1 wherein the SiO_(y) core has athickness of from 20 to 200 nm.
 7. A process for producing the pigmentaccording to claim 3 by alternately coating SiO_(y) flakes with a metaloxide with a high refractive index and a metal oxide with a lowrefractive index in a wet process by hydrolysis of the correspondingwater-soluble metal compounds, by separating, drying and optionallycalcinating the pigment thus obtained.
 8. A process for producing thepigment according to claim 2, wherein SiO_(y) flakes are suspended in anaqueous and/or organic solvent containing medium in the presence of ametal compound and the metal compound is deposited onto SiO_(y) flakesby addition of a reducing agent.
 9. A pigment comprising particleshaving a length of from 2 μm to 5 mm, a width of from 2 μm to 2 mm, anda ratio of length to thickness of at least 2:1, wherein the particlescontain a core with a thickness of from 20 to 200 nm of SiO₂ or asilicon/silicon oxide core obtained by heating SiO_(y) flakes with0.70≦y≦1.80, in an oxygen-free atmosphere at a temperature of at least400° C., having two substantially parallel faces, the distance betweenwhich is the shortest axis of the core, and a material, having a highindex of refraction, or a thin semi-transparent metal layer andoptionally further layers.
 10. (canceled)
 11. Paints, printing inks,textiles, coatings, plastics, cosmetics, glazes for ceramics and glass,which are pigmented with a pigment Pigment according to claim
 1. 12. Apigment according to claim 1, wherein 1.1≦y≦1.8 and the material havinga high index of refraction is a metal oxide.
 13. A pigment according toclaim 2, wherein 1.1≦y≦1.8.
 14. A pigment according to claim 3, whereinthe metal oxide of high refractive index is one or more compoundsselected from the group consisting of TiO₂, ZrO₂, Fe₂O₃, Fe₃O₄, Cr₂O₃,ZnO, an iron titanate, an iron oxide hydrate and a titanium suboxide, ora mixed phase of these compounds.
 15. The pigment according to claim 1,wherein the SiO_(y) core has a thickness of from 50 to 150 nm.
 16. Thepigment according to claim 1, wherein the SiO_(y) core has a thicknessof from 60 to 120 nm.
 17. The pigment according to claim 2, wherein theSiO_(y) core has a thickness of from 20 to 200 nm.
 18. The pigmentaccording to claim 2, wherein the SiO_(y) core has a thickness of from50 to 150 nm.
 19. The pigment according to claim 2, wherein the SiO_(y)core has a thickness of from 60 to 120 nm.
 20. A pigment according toclaim 9, wherein the thickness of the particle core is from 50 to 150nm, 1.1≦y≦1.8 and and the material having a high index of refraction isa metal oxide.
 21. Paints, printing inks, textiles, coatings, plastics,cosmetics, glazes for ceramics and glass, which are pigmented with apigment Pigment according to claim 2.